The present invention relates to containers for storing refrigerated dough. In particular, it relates to dough containers capable of venting internal gasses created by or displaced as a result of the proofing process.
During the manufacture of packaged refrigerated dough products, the dough product is often exposed to oxygen in the headspace within the container for an extended period of time after packaging. When this occurs, the quality of the product deteriorates leaving a product which is unacceptable to consumers. "Headspace" for purposes of this disclosure is the void volume within the container after inserting the product and closing the container.
Many of the quality problems result from the dough being exposed to oxygen or other headspace gasses for extended periods of time. When dough is exposed to oxygen, the dough can become discolored, the product can become deformed and liquids can accumulate in the container wetting the product. Additionally, loud noises can occur when the consumer opens the container. The noise is a result of the presence of compressed headspace gasses within the can.
One of the largest problems caused by refrigerated dough contacting oxygen for extended periods of time is discoloration of the dough. The dough turns a distinct grayish color. This greying is unacceptable to consumers and results in consumer complaints. Although grey dough is safe for consumption, consumers refuse to prepare discolored dough because they believe the dough is spoiled.
Wetness in the product is the result of the collection of liquid at the interface between the gas and the dough within the container. The dough becomes wetted with the collected liquid which may be either oily or milky in appearance. All of the above-identified quality problems are unacceptable to consumers.
Manufacturing dough for refrigerated storage is well known. Examples of refrigerated dough which are purchased and baked at home include dough for preparing bread-like products such as biscuits, loafs, breakfast rolls, pastries, pizza crust, and bread sticks. The dough for these products is prepared by the manufacturer and then packaged in containers suitable for processing, shipping, and storing.
Dough prepared for refrigerated storage are generally chemically leavened. Therefore, dough compositions commonly include a combination of a slow acting leavening acid and an alkaline substance capable of releasing carbon dioxide upon reaction with the leavening acid. The most common systems include either glucono delta lactone or sodium acid pyrophosphate as the acidulant with sodium bicarbonate. Examples of patents which disclose refrigerated dough compositions 25 are Yong et al. U.S. Pat. No. 4,381,315, Matz U.S. Pat. Nos. 3,356,506 and 3,397,064, and Lutz U.S. Pat. No. 3,669,682.
Dough compositions of the type discussed above can be either proofed before or after packaging. "Proofing" for purposes of this disclosure is defined as a step in which the dough increases in volume as a result of leavening. The leavening agents react and expand the dough by approximately to 30 volume percent. After proofing, the dough is further developed by storage in a sealed container at refrigeration temperatures until a point in which the internal pressure of the container has reached a selected equilibrium pressure (typically about 10 psi), and the dough temperature is the same as the temperature of the refrigerated storage area (typically about 45 degrees Fahrenheit).
Proofing of the dough is typically accomplished by first packaging the dough in a container which allows gas to escape until the dough expands to a volume sufficient to completely fill the container. U.S. Pat. No. 3,897,563 to Tucker et al. which is herein incorporated by reference describes a method of proofing and developing of refrigerated dough products. The dough is first packaged to fill between about 70 and about 99 percent of the volume of a spirally wound container. The container is then covered with a cap capable of venting gasses. The filled containers are stored for a period of about 1 to about 6 hours. During this time the leaveners react producing carbon dioxide which expands the dough. After the dough has filled the container, proofing is complete.
Next, the dough is developed. The containers are placed in refrigerated storage for a time sufficient for the internal pressure in the container to build and continue to rise until reaching a target equilibrium pressure of between about 8 and 28 psi. Pressure equilibrium is usually reached between about 8 and about 48 hours.
Containers suitable for packaging and storing refrigerated dough as described above must be able to vent gasses present in the headspace of the can before proofing and gasses produced by the dough during proofing. The container must also be able to withstand internal pressures of up to 40 psi.
One end cap construction known in the art which is capable of venting gasses is shown in cross-section in FIG. 1. Prior art composite container 10 has a single crimp end cap configuration. The container wall 11 is multilayered and is substantially cylindrical. Each end of the container wall has an inner sealing surface 14, an outer sealing surface 16 and an outer edge 17.
The end cap 12 has an inner lip 18 extending over the inner sealing surface 14 and an integrally formed outer lip 20. The outer lip 20 includes an infolded layer 22 which is folded inwardly, abutting the outer lip 20 and extending over the outer sealing surface 16. The outer lip 20 and inner lip 18 are then compressed, squeezing the cylindrical container wall and sealing the dough into the container.
This construction, known in the art as a single crimp end cap, typically allows some gasses to vent from within the container, and does not allow the dough composition to escape. When the dough within the container expands and comes into contact with the end cap 12, or when oil or water plugs the gas escape path, the can seals and pressure begins to build within the container.
Although in theory a single crimp end cap construction is desirable for proofing and developing dough at pressures close to one atmosphere, in practice, the gas escape paths prematurely seal and pressure begins to rise within the container during either proofing, developing, or both.
"Premature sealing" for the purposes of this disclosure includes any sealing of the escape path which occurs before the dough has fully expanded to fill the container and before the dough has been fully proofed. This premature sealing may be partial or total. Even a partial sealing of the gas escape path results in a significant reduction in vent rate and results in premature positive pressure build-up within the container. If the escape path seals before the dough has fully expanded, the gasses present in the headspace are not exhausted, and remain in contact with the dough for an extended period of time, causing quality problems to occur.
Although the inventors do not wish to be bound by any theory of why premature sealing occurs, we believe that there are several potential causes. Water or oil from inside the container may be forced into the venting path and may effectively seal the path, prohibiting gasses from escaping. The composite core layer of the container wall is often formed in part from paper material such as paperboard and may become saturated with either oil or water causing the paperboard to expand. Such an expansion might cause the composite portion of the can to press outwardly and upwardly against the cap and partially or totally seal off the escape path. Another potential cause of premature sealing may result from crimping the end cap too tightly onto the end of the container.
Numerous spirally wound composite can configurations are known for use with refrigerated dough. Typically, they are designed to withstand internal pressures generated by the dough. Several examples of a suitable container designs are described in Culley et al. U.S. Pat. No. 3,510,050, Reid U.S. Pat. No. 3,972,468, Beauchamp U.S. Pat. No. 4,241,834, and Thornhill U.S. Pat. No. 3,981,433. Such containers generally have bodies which include a multilayer spiral wound cylindrical structure having substantially flat, circular single crimp end covers. The container body has a core layer which is formed from a relatively stiff can-grade paperboard. The container body is formed by known spiral winding methods. Adhesively bonded to the inner surface of the core layer is a water and oil impermeable layer. Adhesively bonded to the exterior surfaces of the core layer is a label layer which also protects the core layer from damage due to exposure to high humidity environments, for example.
The cylindrical portion of a spirally wound composite can is continuous and has a smooth edge which contacts the cap. Likewise, the cap is comprised of a substantially flat metal piece which contacts the cylindrical portion of the container by means of a single crimp around the periphery of the cap.